AdblockPlus - subscribe to Easylist or Fanboy
Downthemall! - Download manager, throttle, accelerate, batch
Video DownloadHelper - download flash video
ScreenGrab! - Save Google Maps
Download Statusbar - Keep track of downloads on main window
FlashGot - use with FlashGet
FireFTP - FTP Client
FlashGet - Download Accelerator, throttle downloads, change referrer, shutdown when complete, batch downloads, multiple mirror, use version 1.72. Version 1.73 has a toolbar.
qTorrent - Torrent downloader
Peerblock - selective firewall
FileZilla - FTP Client